Process for manufacturing a semiconductor device including a microelectromechanical structure and an associated integrated electronic circuit and corresponding semiconductor device

ABSTRACT

A process for manufacturing an integrated semiconductor device, envisages: forming a MEMS structure; forming an ASIC electronic circuit; and electrically coupling the MEMS structure to the ASIC electronic circuit. The MEMS structure and the ASIC electronic circuit are integrated starting from a same substrate including semiconductor material; wherein the MEMS structure is formed at a first surface of the substrate, and the ASIC electronic circuit is formed at a second surface of the substrate, vertically opposite to the first surface in a direction transverse to a horizontal plane of extension of the first surface and of the second surface.

BACKGROUND Technical Field

The present disclosure relates to a process for manufacturing asemiconductor device including a MEMS (Micro-Electro-Mechanical System)structure and an associated integrated electronic circuit, and to acorresponding semiconductor device.

Description of the Related Art

Semiconductor devices, for example sensor devices, are known, including:at least one MEMS structure, for example a sensing structure designed togenerate an electrical quantity in response to a detected quantity (suchas an acceleration, an angular velocity, or a pressure); and a coupledintegrated electronic circuit (ASIC, Application-Specific IntegratedCircuit), which integrates appropriate circuit elements for processing(for example, by amplification and filtering) the aforesaid electricalquantity generated by the MEMS structure and supplying an output signal,for example a voltage indicative of the detected quantity.

The MEMS structure and the corresponding ASIC electronic circuit aretypically provided in respective dies of semiconductor material, whichare housed, electrically connected together in a suitable manner, withina same package. The package defines the mechanical and electricalinterface of the integrated semiconductor device towards the externalenvironment, for example, for coupling to a PCB (Printed-Circuit Board)of an electronic apparatus that incorporates the integratedsemiconductor device.

As it is known, generally, manufacturing of the MEMS structure of theintegrated semiconductor device entails manufacturing steps that are notcompatible with the manufacturing of the coupled ASIC electroniccircuit, which typically envisages CMOS (Complementary Metal OxideSemiconductor) process steps; for example, the temperatures, materials,and processing environments envisaged for the MEMS structure may not becompatible with at least some of the CMOS process steps.

For instance, the temperature of epitaxial deposition of a polysiliconlayer starting from which a mobile mass of the MEMS structure isdefined, for example approximately 1100° C., may not be compatible withthe melting point of metallization layers of the ASIC, for exampleapproximately 450° C. in the case of aluminum.

It is, thus, common practice to manufacture separately, with respectiveindependent manufacturing operations, the MEMS structure and thecorresponding ASIC in respective substrates (or wafers) of semiconductormaterial, and subsequently bond together the two substrates (or wafers)with bonding techniques.

FIG. 1 shows an example of integrated semiconductor device 1, of a knowntype, in which a first substrate 2, including a MEMS structure (purelyby way of non-limiting example here comprising a cavity 3 and a membrane4 extending above the cavity 3), is stacked on top of a second substrate5, including an ASIC electronic circuit, within a package 6.

The MEMS structure integrated in the first substrate 2 and the ASICelectronic circuit integrated in the second substrate 5 are manufacturedin a separate and independent way, before the same first and secondsubstrates 2, 5 are stacked on top of one another and bonded by aninterposed adhesive layer 7.

The stacked structure constituted by the first and second substrates 2,5 is arranged on a supporting layer 8 via an adhesive layer, thesupporting layer 8 constituting the base of the package 6 and having atop surface 8 a, to which the second die 5 is attached by a furtheradhesive layer 9, and a bottom surface 8 b, which is in contact with theenvironment external to the package 6 and carries appropriateelectrical-contact elements (not illustrated herein), for example in theform of conductive lands or bumps, designed, for example, for couplingwith a PCB.

The first and second substrates 2, 5 have a respective top surface,provided on which are respective contact pads 10, electrically connectedto the MEMS structure and to the ASIC electronic circuit (in a way thatwill be evident to a person skilled in the field). Further contact pads11 are provided on the top surface 8 a of the supporting layer 8.

First bonding wires 12 electrically connect together, according to theso-called “wire-bonding technique,” the contact pads 10 of the first andsecond substrates 2, 5. Second bonding wires 13 connect electricalcontact pads 10 of the second substrate 5 to the further contact pads11.

Electrical connection between the aforesaid further contact pads 11 andthe electrical-contact elements carried by the bottom surface 8 b of thesupporting layer 8 is obtained by through electrical vias (notillustrated herein) that traverse the entire thickness of the samesupporting layer 8.

A covering element 14 is further arranged above the top surface of thefirst substrate 2, and an insulating coating 15, the so-called molding,or mold compound, for example, epoxy resin, coats said covering element14, the stacked structure of the first and second substrates 2, 5, andthe external portions of the top surface 8 a of the supporting layer 8not coated by the second substrate 5. A top surface of the insulatingcoating 15 constitutes an outer surface of the entire package 6, incontact with the external environment.

The resulting integrated semiconductor device 1, although having ingeneral good electrical performance, thanks in particular to the provenreliability of the coupling via wire bonding between the substrates 2,5, has, however, quite considerable overall dimensions both in ahorizontal direction (transverse to the stacking direction) and in avertical direction (in the stacking direction).

In particular, there are applications, for example for portable orwearable apparatuses, in which it is certainly desirable for theresulting dimensions of the integrated semiconductor device 1 to besmaller.

Even though further bonding solutions between the substrates integratingthe ASIC electronic circuit and the MEMS structure have been proposed,none of these solutions has proven altogether satisfactory.

For instance, FIG. 2 shows a further embodiment of an integratedsemiconductor device, once again designated by 1, of a known type.

In this solution, the first substrate 2, which integrates the MEMSstructure (once again represented schematically), is bonded to thesecond substrate 5, which integrates the ASIC electronic circuit, byaluminum-germanium (Al-Ge) wafer-to-wafer bonding.

In particular, a bonding ring 17, of conductive material, arrangedbetween the top surfaces of the first and second substrates 2, 5, facingone another, in addition to defining the mechanical coupling between thesubstrates 2, 5, defines the mutual electrical connections.

The above embodiment is more compact, both in a horizontal direction andin a vertical direction, thus enabling a corresponding reduction of thedimensions of the integrated semiconductor device 1. However, as will beevident to a person skilled in the field, it is difficult to guaranteehermetic coupling between the substrates 2, 5 and at the same timeelectrical connection by the aforesaid bonding ring 17.

A further solution that has been proposed (see, for example, U.S.2011/095835), envisages that the manufacturing steps of the MEMSstructure are carried out following upon the CMOS processing steps thathave previously led to manufacturing of the ASIC electronic circuit.

In particular, on a top metallization level, which defines the topsurface of the CMOS substrate in which the ASIC electronic circuit isprovided, at a low temperature (in order not to damage the elements ofthe same ASIC electronic circuit), a silicon-germanium (Si-Ge) layer isgrown and subsequently subjected to further manufacturing operations fordefinition of the MEMS structure.

Albeit enabling a further reduction of the dimensions of the integratedsemiconductor device, the above solution is particularly critical, in sofar as the process steps for manufacturing of the MEMS structure maydamage the underlying ASIC electronic circuit; in any case, thissolution is complex, in so far as the above process steps must beprovided by specific arrangements for preserving the integrity of theASIC electronic circuit.

BRIEF SUMMARY

At least one embodiment of the present disclosure solves the problemshighlighted previously, and in particular to provide an improvedsolution for the manufacturing of a semiconductor device including botha MEMS structure and an ASIC electronic circuit made with the CMOStechnique.

Consequently, according to the present disclosure, a process formanufacturing a semiconductor device and a corresponding semiconductordevice are provided.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

For a better understanding of the present disclosure, preferredembodiments thereof are now described, purely by way of non-limitingexample and with reference to the attached drawings, wherein:

FIG. 1 is a schematic cross-sectional view of an integratedsemiconductor device of a known type;

FIG. 2 is a schematic cross-sectional view of a further integratedsemiconductor device of a known type;

FIGS. 3A-3 m are schematic cross-sectional views of an integratedsemiconductor device in successive steps of a manufacturing processaccording to a first embodiment of the present solution;

FIGS. 4a and 4b are schematic cross-sectional views of a package of theintegrated semiconductor device;

FIGS. 5a-5l are schematic cross-sectional views of an integratedsemiconductor device in successive steps of a manufacturing processaccording to a second embodiment of the present solution;

FIGS. 6a and 6b are schematic cross-sectional views of a package of theintegrated semiconductor device;

FIGS. 7a-7j are schematic cross-sectional views of an integratedsemiconductor device in successive steps of a manufacturing processaccording to a third embodiment of the present solution; and

FIG. 8 is a schematic cross-sectional view of a further variant of theintegrated semiconductor device.

DETAILED DESCRIPTION

As will be discussed in detail, one aspect of the present solutiongenerally envisages integrating a MEMS structure and an ASIC electroniccircuit in a same processed substrate (or wafer), includingsemiconductor material and compatible with CMOS or high-speed CMOS(HCMOS) techniques, while maintaining substantially separate anddistinct the manufacturing processes of the MEMS structure and the ASICelectronic circuit, so that no particular arrangements or modificationsare required to the same processes to prevent mutual negative effectsduring the corresponding steps.

In particular, the MEMS structure and the ASIC electronic circuit areprovided at vertically opposite surfaces of the substrate (or wafer)being processed, and interconnection structures are formed through thesubstrate for electrical connection between the MEMS structure and theASIC electronic circuit. During manufacture, thanks to the interpositionof the substrate, the process steps carried out to obtain the MEMSstructure thus do not affect the ASIC electronic circuit, and, likewise,the process steps carried out to obtain the ASIC electronic circuit donot affect the MEMS structure.

The processes used for providing the MEMS structure and the ASICelectronic circuit may thus be, taken by themselves, of a substantiallystandard type, without particular modifications being required forintegration in the same substrate.

With reference first to FIG. 3A a first embodiment of a process formanufacturing an integrated semiconductor device according to thepresent solution is now described.

An initial step of the manufacturing process envisages providing asubstrate 20, having a first surface 20 a and a second surface 20 bopposite to one another in a vertical direction (transverse to a mainhorizontal plane of extension of the first and second surfaces 20 a, 20b).

The substrate 20, in this embodiment of an SOI (Silicon-On-Insulator)type, in this case includes: an active layer 21 a, of silicon, forexample having a thickness of 50-80 μm; an insulating layer 21 b, forexample of silicon dioxide; and a structural layer 21 c, which is alsomade of silicon, for example with a thickness of 500-600 μm.

Through a surface portion of the substrate 20, starting from the firstsurface 20 a, in this case throughout the whole thickness of the activelayer 21 a, interconnection structures 22 are then provided, theso-called vias, as shown in FIG. 3B.

These interconnection structures 22 may, for example, be made, asdescribed in U.S. Pat. No. 6,838,362, which is incorporated herein byreference in its entirety.

Each interconnection structure 22 is in this case constituted by aconnection portion 22 a, here made of silicon, surrounded by aninsulation portion 22 b, which electrically insulates the connectionportion 22 a from the remaining substrate 20.

In particular, the insulation portion 22 b, having for example a ringconformation, is in turn formed by a conductive core 23, for example ofpolysilicon, enclosed in an insulating coating 24, for example ofsilicon oxide, defining an insulation capacitor for electricallyinsulating the connection portion 22 a from the substrate 20.

The manufacturing process then proceeds with manufacturing steps (inthemselves known) for the formation of a MEMS structure (designated by26 in the subsequent FIG. 3K) on the first surface 20 a of the substrate20. The MEMS structure 26 may, for example, define an accelerometer or agyroscope or a different sensor.

In particular, as illustrated in FIG. 3C, manufacture of the MEMSstructure 26 envisages in this case formation of a permanent insulationlayer 27, on the first surface 20 a of the substrate 20 (thus on theactive layer 21 a of the same substrate 20), and of conductive portions28, made, for example, of polysilicon, through the permanent insulationlayer 27, in contact with the connection portions 22 a of theinterconnection structures 22.

Conductive elements 29 are further formed on the permanent insulationlayer 27, which are also for example of polysilicon (designed to formelectrodes and conductive paths of the MEMS structure 26). Inparticular, some of these conductive elements 29 contact respectiveconductive portions 28.

A sacrificial insulation layer 30 is then formed over the conductiveelements 29 and the permanent insulation layer 27. The sacrificialinsulation layer 30 is, for example, made of silicon oxide and may havea thickness of 1.6-1.8 μm.

Through the thickness of the sacrificial insulation layer 30 anchorageelements 31 are then provided, for example, made of polysilicon, whichextend vertically to contact respective conductive elements 29.

An epitaxial layer 32 is then grown on the sacrificial insulation layer30, for example having a thickness comprised between 20 and 60 μm.

According to an aspect of the present solution, an oxide layer 33 isthen formed on the epitaxial layer 32, as illustrated in FIG. 3D; thisoxide layer 33, as described hereinafter, is designed for providing afusion bonding. The oxide layer 33 is further subjected to aplanarization surface treatment.

Next, as shown in FIG. 3E, a first service wafer 34, for example, ofsilicon and having a thickness of 600 μm, is bonded on the oxide layer33. The first service wafer 34 is designed exclusively for functions ofhandling of the substrate 20 during its processing.

The coupled assembly of the first service wafer 34 and substrate 20 isthen subjected to the so-called flip-wafer operation (FIG. 3F) so thatthe second surface 20 b of the substrate 20, and thus the structurallayer 21 c, is accessible for the subsequent processing steps.

As shown in FIG. 3G, the structural layer 21 c is then removed (forexample, by lapping, stopping at the insulating layer 21 b), and theinsulating layer 21 b is subsequently removed, for example by chemicaletching for rendering accessible a working surface 20 b′ of the activelayer 21 a, vertically opposite to the first surface 20 a.

The process then proceeds with CMOS process steps, of a per se knowntype, for obtaining, within the active layer 21 a of the substrate 20,on the aforesaid working surface 20 b′, an ASIC electronic circuit(designated by 36 in the subsequent FIG. 3H), designed to be operativelycoupled to the MEMS structure 26 of the integrated semiconductor device.

It should be noted that these process steps are independent of theprevious steps for obtaining the MEMS structure 26, and may be carriedout without repercussions on the elements previously formed of the sameMEMS structure 26, which is arranged in fact vertically opposite andseparated by the thickness of the active layer 21 a of the substrate 20.

In particular, as shown schematically in FIG. 3H, in a per se knownmanner, the steps of the CMOS process envisage, among others, formationof: functional regions 37 within the active layer 21 a starting from theworking surface 20 b′ (by way of example, doped source and drain regionsof a MOSFET are illustrated, obtained by diffusion of dopant, forexample of an N type in the case where the active layer 21 a has adoping of a P type); an insulation layer 38, which defines, inparticular, the gate oxide of the aforesaid MOSFET, over the workingsurface 20 b; electrode elements 39, over the insulation layer 38,including, for example, a gate electrode of the same MOSFET; and,subsequently, a CMOS multilayer 40 on the working surface 20 b′,constituted by a stack of metallization layers 40 a and interposeddielectric layers 40 b, with interconnection elements 40 c thatelectrical connect, in an appropriate way, metallization layers 40 aarranged on top of one another. The last metallization layer 40 afurther defines a top surface of the CMOS multilayer 40.

As illustrated in the same FIG. 3H, during the same processing steps theelectrical contacts between the ASIC electronic circuit 36 and the MEMSstructure 26, via the interconnection structures 22, are furtherdefined.

In particular, the conductive portions 22 a of the interconnectionstructures 22 are connected to respective electrode elements 39 byconductive elements 41 formed through the insulation layer 38. Theseconductive elements 41, by a respective interconnection element 40 c,are further connected to respective portions of the first metallizationlayer 40 a of the CMOS multilayer 40 (in this way, being appropriatelyconnected to one or more components of the ASIC electronic circuit 36,for example to the aforesaid gate electrode of the MOSFET).

The manufacturing process then proceeds (FIG. 3I), with formation on themultilayer 40 of an oxide layer 43 and then with fusion bonding of asecond service wafer 44, for example of silicon and having a thicknessof 600 μm, on the aforesaid oxide layer 43. Also this second servicewafer 44 is designed exclusively for functions of handling of thesubstrate 20 being processed.

It should be noted that also this bonding, like the previous one, thusdoes not create problems of reliability as regards operation of thedevice, being in fact designed only for handling operations.

Then, a further flip-wafer operation is carried out, following uponwhich the first service wafer 34 is accessible for processing (thesecond service wafer 44 instead constituting the handling base).

The above first service wafer 34, as illustrated in FIG. 3K, is thenremoved (for example, by lapping, stopping at the oxide layer 33), andthe oxide layer 33 is subsequently removed, for example by chemicaletching, for making the epitaxial layer 32 accessible for subsequentprocessing.

At this point, the manufacturing of the MEMS structure 26 is completedwith final processing steps, which are also in themselves known.

In particular (FIG. 3K), through openings 46 are first formed throughthe entire thickness of the epitaxial layer 32, through which a chemicaletch is carried out for removal of the sacrificial insulating layer 30.

This removal, as shown in the same FIG. 3K, entails in particularrelease of suspended elements 47, which are arranged above the activelayer 21 a of the substrate 20, constrained to the same active layer 21a by the anchorage elements 31. In a per se known manner, thesesuspended elements 47 may, for example, constitute inertial masses ofthe MEMS structure 26.

Then, a covering 48 is coupled on the epitaxial layer 32, which coversthe MEMS structure 26 and the through openings 46 (FIG. 3L). Thecovering 48 is bonded to the epitaxial layer 32, for example with theglass-frit bonding technique, by bonding regions 49, which define anempty space above the same epitaxial layer 32.

The manufacturing process envisages at this point final steps forproviding a package for the MEMS structure 26 and the corresponding ASICelectronic circuit 36.

In particular, a further flip-wafer operation is carried out, followingupon which the second service wafer 44 is available for processing, andsubsequently the service wafer 44 is removed, for example via lapping.

As illustrated in FIG. 3M, a passivation layer 50 is formed on the oxidelayer 43, having functions of protection for the underlying ASICelectronic circuit 36, and contact openings 51 are then formed throughthe same oxide layer 44 and passivation layer 50.

Then contact pads 52 are formed within these contact openings, inelectrical contact with respective portions of the last metallizationlayer 40 a, designed to enable electrical contacting of the ASICelectronic circuit 36 from outside the package of the integratedsemiconductor device.

FIG. 4A shows a possible embodiment of a package 54, of a standard landgrid array (LGA) type, for the integrated semiconductor device, heredesignated as a whole by 55.

The package 54 includes a supporting layer 56, on which the covering 48is bonded, for example using adhesive, and a molding 57, which coats thesupporting layer 56 and the stack formed by the MEMS structure 26 and bythe corresponding ASIC electronic circuit 36, made starting from thesame substrate 20. A top surface of the aforesaid molding 57 in thiscase constitutes a top surface of the package 54, in contact with theexternal environment.

Electrical bonding wires 58 electrically connect the contact pads 52 tofurther contact pads 59 carried by the supporting layer 56, via thewire-bonding technique.

The aforesaid further contact pads 59 are further connected byelectrical through vias (here not illustrated), which traverse theentire thickness of the supporting layer 56, to electrical-contactelements 60 carried by the bottom surface of the supporting layer 56(which in this case constitutes the bottom base of the package 54, incontact with the external environment).

FIG. 4B shows a further embodiment of the package 54 of the integratedsemiconductor device 55, of a ball grid array (BGA) type withoutmolding.

In this case, the covering 48 itself defines a surface of the package54, in contact with the external environment, and the passivation layer50 that overlies the CMOS multilayer 40 of the ASIC electronic circuit46 defines, itself, the outer opposite surface of the package 54 (whichthus does not comprise any additional supporting or molding layer).

The electrical-contact elements 60, in this case in the form ofconductive bumps, electrically contact the contact pads 52 on the outersurface of the package 54.

A second embodiment of the present solution is now described, whichdiffers in that it envisages a different process for manufacturing theMEMS structure 26, which is also of a per se known type (the MEMSstructure 26 defines in this case, for example, a pressure sensor). Nosubstantial modifications are, instead, envisaged in the flow ofintegration of the MEMS structure 26 with the associated ASIC electroniccircuit 36 in the same substrate 20.

As shown in FIG. 5A, the process starts once again with the provision ofthe substrate 20, of an SOI type.

In this case, elements constituting the pressure sensor defined by theMEMS structure 26 are provided in the active layer 21 a of the substrate20.

In particular, as shown in FIG. 5B, at least one buried cavity 60 isfirst provided within the active layer 21 a, separated from the firsttop surface 20 a of the substrate 20 by a membrane 61. Further providedare surface diffusions for formation of piezoresistor elements 62 in asurface portion of the membrane 61.

As described previously, interconnection structures 22 are formedthrough the active layer 21 a, in this case laterally with respect tothe arrangement of the buried cavity 60 and the membrane 61.

The manufacturing process then proceeds, as described previously, with:formation of the oxide layer 33 on the first surface 20 a of thesubstrate 20 (FIG. 5C); subsequent bonding of the first service wafer 34on the oxide layer 33 (FIG. 5D); wafer flipping (FIG. 5E); removal ofthe supporting layer 21 c and of the insulating layer 21 b of thesubstrate 20 (FIG. 5F); and subsequent CMOS process to obtain the ASICelectronic circuit 36 starting from the working surface 20 b′ of theactive layer 21 a of the same substrate 20, and also to obtainelectrical contacts between the ASIC electronic circuit 36 and the MEMSstructure 26 through the interconnection structures 22 (FIG. 5G);subsequent bonding of the second service wafer 44 on the oxide layer 43previously formed on the CMOS multilayer 40 (FIG. 5H); and waferflipping, and removal of the oxide layer 43 and second service wafer 44for processing of the first surface 20 a of the substrate 20 (FIG. 5I).

The manufacturing process then envisages the steps of completion of theMEMS structure 26 integrated in the substrate 20, which include in thiscase (FIG. 5J): formation of a surface insulation layer 64, for exampleof TEOS (Tetraethyl Orthosilicate); deposition and definition of aconductive layer 65 on the surface insulation layer 64 and withintrenches that traverse the same surface insulation layer 64 to contactthe piezoresistor elements 62 and also the connection portions 22 a ofthe interconnection structures 22; and formation of a passivation layer66 on the conductive layer 65.

In a way similar to what has been described previously, themanufacturing process then proceeds (FIG. 5K) with coupling of thecovering 48, in this case on the passivation layer 66, through which inthis case access openings 68 are provided for enabling pressure wavescoming from the external environment to reach the MEMS structure 26integrated in the substrate 20.

At this point (FIG. 5L), the structure being processed is flipped, thesecond service wafer 44 is removed, and the contact pads 52 forcontacting the respective portions of the last metallization layer ofthe CMOS multilayer 40 are formed.

The package 54 of the integrated semiconductor device 55 also in thiscase (as described in detail previously) may be, for example, of astandard LGA type, as illustrated in FIG. 6A, or else of a BGA typewithout molding as illustrated in FIG. 6B.

With reference first to FIG. 7A, a third embodiment of the presentsolution is now described, which differs from the one illustratedpreviously in that it starts from a standard substrate, for example witha doping of a P type, instead of an SOI composite substrate. As regardsformation of the MEMS structure 26, this further embodiment does notdiffer, instead, from the first embodiment previously described.

As shown in FIG. 7B, in a surface portion of the substrate 20 at thefirst surface 20 a, designated by 21 a by analogy with what has beendiscussed previously, the interconnection structures 22 are provided,here formed by the connection portion 22 a electrically insulated fromthe substrate 20 by the insulation portion 22 b (here constituted by asimple vertical structure of silicon oxide or other insulating materialthat extends in depth throughout the thickness of the surface portion 21a).

On the first surface 20 a of the substrate 20, the permanent insulationlayer 27 is then formed, as discussed previously, with the conductiveportions 28 that traverse the permanent insulation layer 27 to contactthe connection portions 22 a of the interconnection structures 22 (FIG.7B).

The manufacturing process then proceeds, as described previously, withthe steps of formation of the MEMS structure 26 (FIG. 7C), whichenvisages also in this case formation of: the conductive elements 29 onthe permanent insulation layer 27; the sacrificial insulation layer 30,on the conductive elements 29 and on the permanent insulation layer 27;the anchorage elements 31 through the thickness of the sacrificialinsulation layer 30; and the epitaxial layer 32 on the sacrificialinsulation layer 30.

The oxide layer 33 is then formed on the first surface 20 a of thesubstrate 20 and the first service wafer 34 is then bonded on the sameoxide layer 33.

Next (FIG. 7D), the wafer is flipped and an etch of the substrate 20 isperformed starting from the second surface 20 b, until the surfaceportion 21 a and the interconnection structures 22 are reached, thusdefining the working surface 20 b′, starting from which the CMOSprocessing steps will then be carried out.

As illustrated previously, the manufacturing process then proceeds with:the CMOS process steps for providing the ASIC electronic circuit 36starting from the aforesaid working surface 20 b′, and also electricalcontacts between the ASIC electronic circuit 36 and the MEMS structure26 through the interconnection structures 22 (FIG. 7E); subsequentbonding of the second service wafer 44 on the oxide layer 43 previouslyformed on the CMOS multilayer 40 (FIG. 7F); and flipping of the wafer,and removal of the oxide layer 43 and the second service wafer 44 (FIG.7G).

The last processing steps are thus performed leading to formation of theMEMS structure 26, as illustrated in FIG. 7H, and to subsequent couplingwith the covering 48 (FIG. 7I).

The structure being processed is then flipped again for removing thesecond service wafer 44 and defining the contact pads 52 for contactingthe respective portions of the last metallization layer of the CMOSmultilayer 40 (FIG. 7J).

In a way not illustrated herein, the process proceeds with formation ofthe package 54 of the integrated semiconductor device 55, in a wayaltogether similar to what has been discussed previously.

The advantages of the solution proposed emerge clearly from the previousdescription.

In particular, the solution described makes it possible to obtain amarked reduction in the horizontal dimensions (in the plane) and in thevertical dimension (out of the plane) of the resulting integratedsemiconductor device 55.

The MEMS structure 26 and the CMOS electronic circuit 36 are provided ina same substrate 20 and may possibly be manufactured in a sameproduction environment.

In general, the solution described affords an evident advantage in termsof manufacturing costs.

Moreover, further advantages are obtained in terms of performance,thanks to the reduction of the (capacitive and inductive) parasiticcomponents in the electrical connection between the MEMS structure 26and the ASIC electronic circuit 36, and to the consequent reduction ofthe noise generated, as well as in terms of reliability, thanks to thefact that the electrical connection between the MEMS structure 26 andthe ASIC electronic circuit 36 is obtained with planar techniques at thefront-end level, instead of being obtained with bonding techniques.

Finally, it is clear that modifications and variations may be made towhat has been described and illustrated herein, without therebydeparting from the scope of the present disclosure.

In particular, it is evident that the process described may findadvantageous application also in the case where different technologiesare used for manufacturing the MEMS structure 26 and/or the associatedASIC electronic circuit 36.

It is likewise evident that further types of package 54 may be envisagedfor housing the MEMS structure 26 and the ASIC electronic circuit 36,integrated starting from the same substrate 20.

Furthermore, different embodiments may be envisaged for theinterconnection structures 22, through the substrate 20, designed toenable connection between the MEMS structure 26 and the associated ASICelectronic circuit 36.

For instance, as illustrated in FIG. 8, the connection portion 22 a ofthe interconnection structures 22, electrically insulated from thesubstrate 20 by the insulation portion 22 b (obtained once again by asimple vertical structure of silicon oxide or other insulating materialthat extends in depth through the thickness of the surface portion 21 a)may include a vertical column of conductive material, in the examplepolysilicon.

In this case, the electrical contact with the first metallization layer40 a of the multilayer 40 of the CMOS structure of the ASIC electroniccircuit 36 may be defined directly by the connection structure 22 and byan interconnection element 40 c, which extends between a terminal end ofthe same interconnection structure 22, at the working surface 20 b′, andthe first metallization layer 40 a (as shown once again in FIG. 8);advantageously, this electrical contact is of an ohmic type.

The various embodiments described above can be combined to providefurther embodiments. These and other changes can be made to theembodiments in light of the above-detailed description. In general, inthe following claims, the terms used should not be construed to limitthe claims to the specific embodiments disclosed in the specificationand the claims, but should be construed to include all possibleembodiments along with the full scope of equivalents to which suchclaims are entitled. Accordingly, the claims are not limited by thedisclosure.

1. A process for manufacturing an integrated semiconductor device,comprising: forming a MEMS structure on a first surface of a substrateincluding semiconductor material; forming an ASIC electronic circuit ona second surface of said substrate, vertically opposite to said firstsurface, in a direction transverse to a horizontal plane of extension ofsaid first surface; and electrically coupling said MEMS structure tosaid ASIC electronic circuit.
 2. The process according to claim 1,wherein electrically coupling said MEMS structure to said ASICelectronic circuit comprises forming interconnection structures, whichextend vertically through a first portion of said substrate startingfrom said first surface.
 3. The process according to claim 2, comprisingremoving a second portion of said substrate, vertically opposite to saidfirst portion, so as to define said second surface and to make saidinterconnection structures accessible at said second surface, saidinterconnection structures thereby having a first end at said firstsurface and a second end at said second surface; wherein forming saidASIC electronic circuit is performed at said second surface afterremoving said second portion of said substrate.
 4. The process accordingto claim 3, wherein electrically coupling said MEMS structure to saidASIC electronic circuit further comprises forming at least oneconductive path between the second end of at least one of saidinterconnection structures and at least one conductive element of saidASIC electronic circuit.
 5. The process according to claim 3, whereinforming said MEMS structure comprises carrying out first processingsteps of manufacturing of said MEMS structure at said first surface;further comprising, after carrying out said first processing steps,bonding a first service wafer over said MEMS structure, and verticallyflipping said substrate; wherein removing said second portion of saidsubstrate is carried out after said flipping step.
 6. The processaccording to claim 5, further comprising, after forming said ASICelectronic circuit, bonding a second service wafer over said ASICelectronic circuit and once again flipping said substrate; and whereinforming said MEMS structure further comprises, after said step of onceagain flipping said substrate: removing said first service wafer fromsaid first surface; and carrying out second processing steps of saidMEMS structure.
 7. The process according to claim 6, wherein said first,or second, processing steps of said MEMS structure comprise forming atleast one conductive path between the first end of at least one of saidinterconnection structures and at least one element of said MEMSstructure.
 8. The process according to claim 6, wherein said firstprocessing steps comprise forming a sacrificial layer over said firstsurface and forming an epitaxial layer on said sacrificial layer; andwherein said second processing steps comprise forming through openingsthrough said epitaxial layer, and carrying out a chemical etch thatremoves said sacrificial layer and defines at least one suspendedelement above said substrate.
 9. The process according to claim 6,wherein said first processing steps comprise forming at least one buriedcavity within the surface portion of said substrate, a membranesuspended above the buried cavity, and piezoresistive elements in saidmembrane; and wherein said second processing steps comprise forming saidconductive path between the first end of at least one of saidinterconnection structures and at least one of said piezoresistiveelements of said MEMS structure.
 10. The process according to claim 1,wherein forming said ASIC electronic circuit comprises forming a CMOSmultilayer over said second surface.
 11. The process according to claim1, wherein said substrate is of an SOI type, and said surface portion isan active layer of the SOI substrate.
 12. The process according to claim1, further comprising coupling a covering over said MEMS structure.13-18. (canceled)
 19. A process for manufacturing an integratedsemiconductor device, comprising: forming a MEMS structure on or in afirst surface of a semiconductor layer; forming an ASIC electroniccircuit on or in a second surface of the semiconductor layer, verticallyopposite to said first surface, in a direction transverse to ahorizontal plane of extension of said first surface; and forminginterconnection structures that extend vertically through thesemiconductor layer and electrically couple the MEMS structure to theASIC electronic circuit.
 20. The process according to claim 19, furthercomprising vertically flipping the semiconductor layer between formingthe MEMS structure and forming the ASIC electronic circuit.
 21. Aprocess for manufacturing an integrated semiconductor device,comprising: forming electrically conductive interconnection structuresextending through a silicon semiconductor layer of asilicon-on-insulator (SOI) substrate that also includes a supportinglayer and an insulating layer; forming a MEMS structure on a firstsurface of the silicon semiconductor layer, wherein forming the MEMSstructure comprises carrying out first processing steps of manufacturingthe MEMS structure on the first surface; bonding a first service waferover said MEMS structure, and vertically flipping the SOI substrate;removing the supporting layer and insulating layer after verticallyflipping the SOI substrate, thereby exposing a second surface of thesilicon semiconductor layer, vertically opposite to the first surface;and forming an ASIC electronic circuit on the second surface of thesilicon semiconductor layer, the ASIC electronic circuit beingelectrically coupled to the MEMS structure by the interconnectionstructures.
 22. The process according to claim 21, wherein bonding thefirst service wafer over said MEMS structure, and vertically flippingthe SOI substrate are performed after carrying out the first processingsteps.
 23. The process according to claim 21, further comprising, afterforming the ASIC electronic circuit, bonding a second service wafer overthe ASIC electronic circuit and once again flipping the SOI substrate,wherein forming the MEMS structure further comprises, after once againflipping the SOI substrate: removing the first service wafer from thefirst surface; and carrying out second processing steps of the MEMSstructure.
 24. The process according to claim 23, wherein the firstprocessing steps comprise forming a sacrificial layer over the firstsurface and forming an epitaxial layer on the sacrificial layer; andwherein said second processing steps comprise forming through openingsthrough the epitaxial layer, and carrying out a chemical etch thatremoves said sacrificial layer and defines at least one suspendedelement above the silicon semiconductor layer.
 25. The process accordingto claim 23, wherein bonding the second service wafer over the ASICelectronic circuit is performed before once again flipping the SOIsubstrate.
 26. The process according to claim 21, wherein forming theASIC electronic circuit on the second surface of the siliconsemiconductor layer includes forming a CMOS multilayer on the secondsurface of the silicon semiconductor layer and forming the ASICelectronic circuit in the CMOS multilayer.